Powdery Mildew Treatment

Has that white powder on the leaves of your favorite plants got you down? Take heart, mildew is not a severe threat to most plants. Mildew is a common, rarely fatal disease which affects many different types of plants.

Eventually, most gardeners will look for a mildew removal strategy. The best strategy combines control and treatment of mildew problems.

Powdery mildew is a fungal disease that causes patches of white to gray powder on the leaves, stems, fruit, or flowers of infected plants. These patches may grow to cover the entire surface on both sides of leaves. Different fungi causes the disease on different plants, but all strains are similar in appearance. On more susceptible types of plants, the mildew will cause leaves to yellow and prematurely drop, stunted or deformed plant growth, and eventual plant decline. Some plants, such as Lilac, seem to survive the fungus with little damage and yearly infections may be ignored.

Mildew thrives in cool, damp conditions with poor air circulation. Good cultural practices can usually control the problem.
• The first step is to select healthy, mildew resistant plants. Many varieties of mildew resistant plants are available. Buy only top quality plants as unhealthy plants are more susceptible of infection.
• Plant susceptible types of plants in full sun. Phlox, roses, cucumbers, and other plants prone to mildew should be planted in well-drained soil where they will receive a minimum of six hours sun a day.
• Do not crowd plants. Good air circulation will discourage the disease.
• Prune infected parts of plants and destroy. Rake the area around the plant to remove any debris. Do not toss infected plant materials into your compost pile. Spores never stop reproducing spores, and they overwinter on diseased plant material. New spores are carried by the wind, so destroying infected leaves is essential to stopping the disease from spreading.

Unlike other fungi, mildew does not require water on the plant surface in order to germinate. Powdery mildew does not like water; a daily spray from the hose can help remove the mildew. Spray plants in the morning, so they have plenty of time to dry before the evening dew or other fungal problems, such as black-spot, may develop.

Another option many gardeners use is a simple home-made baking soda solution to control mildew. The baking soda raises the pH of the leaf, making it unsuitable for growth of mildew spores. Be sure to spray both the upper and underside leaf surfaces. The recipe for baking soda spray is:
• 1 gallon water
• 1 teaspoon baking soda
• A few drops of liquid dish soap

Add water to your sprayer first to help avoid excessive foaming of the solution. The dish soap is essential to help the spray stick to the plant.

Milk seems to be a natural germicide and contains several naturally occurring salts and amino acids which inhibit the disease. Scientists are not sure how milk controls the disease, but it appears to boost the immune system of susceptible plants. To treat your garden with milk, mix one part milk to nine parts water and spray plant surfaces weekly.

Any milk, whole or skim, may be used, but the low fat content of skim milk will help reduce the chances of the spray causing odors.

Mildew can cause significant damage on some plants. Thus, a chemical control may become necessary. Because this is a widespread problem there are many commercial fungicides readily available. Spray treatments should begin at the first sign of infection for the best results.

Spray regularly, more often during cool damp periods. Be sure to cover all surfaces of the plant.

Fungicides generally recommended to control powdery mildew include: Triadimefon, Triforine, Thiophanate-methyl, sulfur, Potassium bicarbonate and Propiconazole.

Not all of these treatments are acceptable for edible plants. Carefully read fungicide labels to find which is right for your particular needs.

For a complete cure of the disease, address the issues that cause it and treat existing infections. This should remove the mildew from your garden and keep it away for good.